Controlling the transmitter powers in wireless communication networks provides multiple benefits. It allows interfering links sharing the same radio channel to achieve required quality of service (QoS) levels, minimizing the power spent in the process and extending the battery life of mobile users. Moreover, by judiciously using power to achieve their QoS goals, interference is mitigated and the network capacity increases. The benefits of power control have attracted substantial research attention. Most of the research, however, has focused on voice-oriented ‘continuous’ traffic, which is dominant in current generation wireless networks.
Next generation wireless networks are currently being designed to support intermittent packetized data traffic, beyond the standard voice-oriented continuous one. Such support is needed for the delivery of sophisticated information services over tetherless wireless channels (for example, Web browsing on a mobile laptop computer). The problem of power control in this new environment of packetized data traffic is not well understood. Early preliminary studies have not addressed several important aspects of the problem.
The transmitter faces the following problem in controlling its power. When the transmitter observes high interference in the channel, it recognizes that it will have to spend a lot of power (actually energy) to overcome the interference and transmit a packet successfully to the receiver. Therefore, it would be better to back off, buffer the traffic and wait for the interference to subside before it transmits to clear the buffer. However, as it has backed off, the buffer is filling up with new packet arrivals and delay rises, which pushes the transmitter to become power-aggressive in order to reduce its backlog. There are many transmitters sharing the channel, each one observing only its local interference (at its intended receiver) and its backlog level. The interference is responsive to transmitter actions. Indeed, a power-aggressive transmitter may cause some other to go into a backoff mode or become also aggressive. For voice-oriented continuous traffic the previous situation cannot be a dominant one, since only minimal ‘elastic’ buffering can be tolerated due to the delay-sensitive nature of the traffic.